Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Beyond the readOnly/idempotent/non-destructive annotations, it discloses non-obvious behavior: rows of the author's own principal, banned players, and rows below the board min_trust are omitted; ties share a rank; and Ringout's elo board reads the live all-time verified arena Elo. This is exactly the kind of hidden filtering the annotations cannot convey.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

A single dense paragraph that front-loads the return shape before parameters and constraints. It is tightly packed with no filler, though the run-on field enumeration is somewhat abbreviated and could benefit from minor structure.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description carries the return shape (field names for rows), default/max for limit, tie behavior, visibility rules, and the special-case Elo board, so nothing needed to interpret results is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so baseline is 3, but the description adds meaning the schema lacks: around returns '10 rows either side' (schema only says 'rows around'), kind recomputes ranks within the filter, and period's default is the board's kept period. Only limit merely restates the schema.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb (get) and resource (leaderboard), gives the exact return record shape {period_start, count, rows[{rank, player, kind, value, trust}]}, and scopes it to 'one board of a game'. An agent knows exactly what this returns without opening the schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Provides clear operational context: how period is chosen ('one the board keeps; default its first'), how kind re-ranks, and that around switches to a window around a player. It never names the obvious alternative get_rankings or states when-not to use this, so it stops short of full routing guidance.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.